a. Field of the Invention
The invention relates generally to jigs for guiding the bits of drills, routers and the like to locations on a work surface, and more particularly to jigs specifically designed to facilitate in the boring and routing of a door in preparation for the installation of a door knob assembly or the like.
b. Prior Art
To install a door knob assembly or dead-bolt lock in a new door it is necessary to first prepare the door by boring and routing holes and recesses receptive to the assembly. The holes must be aligned with respect to each other in a predetermined manner and within certain tolerances so that the mass-produced lock assembly will correctly fit into the door.
For instance, for the most common type of door knob assembly, a bore is formed into the side edge of a door for receiving a latch bolt, and a second bore is formed between two opposing sides of the door to receive a bolt retracting mechanism, such as a key or knob. If the first and second bores are not properly aligned the door knob assembly will not fit therein, which often means that an expensive door must be replaced or reworked. Furthermore, even if the lock assembly can be fitted into the bores, if the bores were not formed accurately the assembly may bind or improperly latch, resulting in unsatisfactory performance.
Another material removal step necessary for the installation of a standard door knob assembly is the routing of the edge of the door around the latch bolt bore for the installation of an edge plate. The edge plate must reside in such a routed depression so that it does not strike the door jamb when the door is closed.
For a person to hand craft the various bores and depressions as described above, he or she would require a great deal of experience and skill. Because of this fact, various persons have developed prior art devices to aid in the preparation of the various bores and routed depressions that are necessary for the installation of a door knob assembly. One example of a prior boring and routing jig for doors is disclosed in U.S. Pat. No. 3,392,607 of E. Gieseke which teaches a jig having a pair of boring guide plates clamped to opposite sides of a door and hinged members for guiding the bits of boring tools or routers to the edge of the door.
In U.S. Pat. No. 3,700,344, A. T. Grumbach discloses a mortising device comprising a frame positionable over the edge of a door and a carriage slideably mounted to the frame. The carriage guides a drill to a series of vertically related positions along the edge of the door to mortise a vertical slot shape for receiving the door latch of a locking mechanism.
These and other jigs found in the prior art are relatively special purpose tools. For instance, some jigs of the prior art include template members which are semipermanently attached to the jig by a plurality of assembly screws. It would be very difficult to use such jigs for an unusual or nonstandard door knob assembly. Other jigs can only be used to mortise holes in the edges of doors and are not adapted to guide boring tools into the sides of doors.